The goal of the proposed research is to develop methods for liquid storage of platelets for at least five days so that there is negligible difference in their viability and function when compared to fresh platelets. We will use studies of 51chromium-labelled platelets in normal volunteers to document viability after storage and template bleeding time studies in thrombocytopenic patients to document preservation of function. During storage, platelets develop functional and biochemical abnormalities. In the patient studies, we will determine if these abnormalities can be corrected during circulation in vivo. Studies will also be carried out to determine the causes of these abnormalities and how they might be prevented. We have developed quantitative measurements which reflect platelet size, shape, and morphology. These measurements performed after storage will be correlated with viability measurements using the 51chromium technique. Hypoxia and fall in pH are two major causes of platelet damage during storage. We will correlate morphologic measurements with measurements of pH, pO2, adenine nucleotide metabolism, and glycolysis to determine the mechanisms of this damage.